Guided Notes about Seawater Chapter 15, Section 2.

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  • Guided Notes about SeawaterChapter 15, Section 2

  • 1. Seawater is a solution of about 96.5% water and 3.5% dissolved salts. The most abundant salt in seawater is sodium chloride (NaCl).

  • 2. Most elements on Earth are present in seawater in the form of ions.

  • Define salinity and state how it is expressed : Salinity is a measure of the amount of dissolved salts in seawater. It is expressed as grams of salt per kilogram of water, or parts per thousand.

  • 4. The sources of salts in seawater are volcanic eruptions and the weathering of crustal rock.

  • 5. Salts are removed from seawater through precipitation near arid, coastal regions. Marine organisms also remove ions from seawater to build their shells, bones, and teeth.

  • 6. Seawater is denser than freshwater because salt ions are heavier than water molecules. The density of seawater varies depending on its salinity and temperature.

  • 7. Variations in salinity also cause the freezing point of seawater to be lower than freshwater. Seawater freezes at -2C

  • 8. The average surface temperature of ocean water is 15 degrees Celcius, but temperatures decrease significantly with depth, so that deep ocean water is always cold, even in tropical oceans.

  • 3 layers of the ocean, based upon temperature variations: Warm, sunlit surface layer, 100 m. thickA transitional layer, the thermocline, in which temperatures decrease rapidly with depth.The bottom layer is cold and dark, with near freezing temperatures


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